1. Field of the Invention
The present invention relates to the field of switched telephony, and more particularly, to a method and system for providing a selectable continuous tone source from a service node to an end user.
2. Background of the Invention
Many Advanced Intelligence Network (AIN) telephone services use the capabilities of a service node (also referred to as a service circuit node) for intelligent call routing. In a typical routing scenario, the service node accepts an incoming call, places an outgoing call in response to the incoming call, and connects the incoming call to the outgoing call. Usually, once the calls are connected, the service node transfers the connected call to a service switching point to disencumber the service node (which is a more limited intelligent network resource). To transfer the connected call, the service node must place the incoming and outgoing calls on hold and transfer them to the service switching point with connection instructions, at which point the service switching point re-establishes the connection. This transfer typically occurs immediately after the service node has executed its intelligent routing functions and before any voice, data, or other communication is conducted over the completed connection.
The principal drawback to this routing strategy is a delay associated with the transfer from the service node to the service switching point. Depending on the particular type of AIN platform, the transfer may last up to three seconds. During this period, when both the incoming and outgoing calls are on hold, the customers on either side of the communication hear silence. As a result, the customers may become confused, mistakenly think the call has been disconnected, and hang up. This possibility is especially true for the calling party who has dialed a number only to experience an extended period of silence. Obviously, such a call switching deficiency severely detracts from any telephone service that uses this service node transfer and reduces the likelihood that a customer will subscribe to the service.
In addition to the call transfer problem, service nodes also put calls on hold to perform other functions, such as looking up data or communicating with other AIN components, e.g., service control points. An AIN service such as voicemail could present this situation. In such a case, the period on hold lasts as long as it takes the service node to process the information. Without connecting a music-on-hold source to the call during the processing, the customer hears silence while the service node has the call on hold.
Telephone service providers (hereinafter, referred to as “Telcos”) have attempted to address the on-hold silence by connecting the calls to a music-on-hold source during the transfer or processing period. Traditionally, the music-on-hold source is a standard audible ringing tone source generated at a central office. FIG. 1 illustrates this architecture. Audible ringing is the typical sound heard after dialing a telephone number, consisting of two seconds of ringing followed by four seconds of silence. Unfortunately, the four seconds of silence is often greater than the on-hold period during a call transfer (approximately three seconds) or during a processing function (duration varies). Thus, even with audible ringing connected to the on-hold calls, the customer often hears just a portion of a ring or no ringing at all. In either case, the customer could still possibly be confused and hang up. Moreover, because it is the caller who is most likely to be confused, and not the subscriber (the called party), the Telco does not have the opportunity to explain this idiosyncrasy of the service to avoid the confusion. Thus, providing audible ringing for music-on-hold fails to solve the problem.
Telcos provide audible ringing through a physical connection to a standard ringing tone plant in a central office. The primary purpose of the tone plant is to provide the audible ringing heard after placing a call. The Telcos use the tone plant for music-on-hold only to take advantage of an existing resource. As an alternative to audible ringing, a Telco could develop a different ringing or tone pattern. However, the Telco would have to consult with an outside vendor, at considerable expense, to create a new type of ringing tone plant source. In addition, the Telco would have to create a new plant source for each type of tone source it desired.
Another drawback to using a tone source generated by the central office concerns the prevalence of equipment failures and the lack of alarming capabilities. Providing the tone source with the central office may require a physical connection to manufacturer discontinued equipment. Such discontinued equipment is prone to irreparable failure because of its age and the fact the manufacturer no longer produces the discontinued equipment or components of the equipment. Further compounding this reliability problem, if the central office tone source does fail, the central office has no means for alarming the customer about the failure. Thus, the customer would not be aware that the tone source is unavailable and would again be left with silence during the on-hold period.
Other solutions to on-hold silence present further drawbacks. Telcos can provide a music-on-hold tone source provisioned on customer premises equipment or on other tone generating equipment connected to the central office (e.g., radio playing). FIG. 2 shows the architecture for this solution. Although this solution allows a customer to customize the on-hold tone source, the architecture requires a permanent, dedicated line from the central office to the customer premises equipment. Because the line is dedicated, multiple customers cannot share the tone source. In addition, the customer is burdened with the expense and responsibility of continuously monitoring the tone source for failure situations.